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Thread: Need help w/tenons on curved piece

  1. #16
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    The answer on the eveness of a symetrical curve can only be gotten at after the curve is chosen. What I mean is that I would do it differently for an elipse, than a simple arch, than a segmented arch, than a compound arch. Let me know which you choose and I'll offer appropriate advice. The way I do it most often is a bow arch referenced to 3 points in space. But when I did an ellipse, that was a lot more complex. A compound arch is a middle ground. Between the two in terms of difficulty. All are viable however.

    As to the more general comment on fairing the piece off the bandaw, I use a spokeshave. Most probably use a router table and pattern bit.
    Shawn

    "no trees were harmed in the creation of this message, however some electrons were temporarily inconvenienced."

    "I resent having to use my brain to do your thinking"

  2. #17
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    Dave Richards - Mahalo for posting that video, great concept. Seems to me to be a really simple, solid solution and one I will be using in the future.

  3. #18
    Quote Originally Posted by Shawn Pixley View Post
    The answer on the eveness of a symetrical curve can only be gotten at after the curve is chosen. What I mean is that I would do it differently for an elipse, than a simple arch, than a segmented arch, than a compound arch. Let me know which you choose and I'll offer appropriate advice. The way I do it most often is a bow arch referenced to 3 points in space. But when I did an ellipse, that was a lot more complex. A compound arch is a middle ground. Between the two in terms of difficulty. All are viable however.

    As to the more general comment on fairing the piece off the bandaw, I use a spokeshave. Most probably use a router table and pattern bit.
    Thanks Shawn. I'm going with a simple arch. That is an arch form that is not mathematically an ellipse and not round but kind of a shallow flowing arch.

  4. #19
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    I've found that making a pattern of the shape through half of the pattern and then flopping the pattern will keep your pattern symmetrical.

  5. #20
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    Quote Originally Posted by Ron Corselli View Post
    Thanks Shawn. I'm going with a simple arch. That is an arch form that is not mathematically an ellipse and not round but kind of a shallow flowing arch.
    Typically what you describe is a segmented arch. This is an arc of a circle whose springpoints are not at a tangent to the circle and to the vertical "collumn." In other words, less than half a circle. A full arch is one where the springpoints are at a tangent to the circle at the vertical column. In other words, it is half a circle or a barrel arch.

    Regardless of nomeclature, when you have any arch that is a portion of a circle, the easiest way is to use a circle jig with your cutting tool (router, saw, etc...). That works if the radius is say 6' or less. A thirty foot radius is impractical in woordworking using a jig and router.

    The alternative is a bent member or bow to mark out the arc. Assuming you can establish both springpoints and the height, when you bend a piece of lath over these three points, you will have something closely approximating a circular arc. I suspect most of us create our arcs this way. You can build a jig that is simple as a 4-6' piece of lath with one end permanantly attached to a string. After bowing the lath, the other end of the string can be tied to the loose end of the lath. This will hold the "arc." The arc can be drawn on your template or the piece itself. I have a number of arc templates I have used for different projects as well as a shop made "bow." If you create a clean template, after marking the stock, flip the template over and you will see if you are symetrical or not.
    Shawn

    "no trees were harmed in the creation of this message, however some electrons were temporarily inconvenienced."

    "I resent having to use my brain to do your thinking"

  6. #21
    The bowed material arch technique is effective and esthetic. Thanks everyone for your help. On to the project!

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